The present invention relates to an arrangement for mounting the deflection system of a color-picture tube of the shadow-mask type, the deflection system consisting of a ferrite toroidal core and two pairs of coils, one for horizontal and one for vertical deflection, and being connected, in a predetermined alignment with the electron-gun system and the screen, with the envelope on the side facing the screen.
Some of the modern types of color-picture tubes are supplied by the manufacturer with the deflection system assembled and adjusted. To do this, the electromagnetic deflection system is mounted on the envelope to ensure the desired accurate position relation between the magnetic deflection system, the electron-gun system, and the screen of the picture tube. As described in U.S. Pat. No. 3,566,321, the deflection system was first bonded to the envelope by filling the space between the envelope and the magnetic deflection system with a curable plastic adhesive.
Such filling involves an uneconomic consumption of adhesive, as is described in the German published patent application (DT-AS) No. 2,342,052. In addition, however, the air circulation between the envelope and the deflection system is obstructed, which results in higher temperatures and in a shorter life expectancy. Furthermore, this leads to an extremely rigid design with high internal stresses which may result in the envelope and/or the magnetic deflection system breaking in case of changes in temperature. To overcome this problem, a maximum of only 20% of the space between the envelope and the magnetic deflection system is filled with a thermoplastic, as is disclosed in the German published patent application (DT-AS) No. 2,342,052. This permits a certain air circulation, and the internal stresses are slightly reduced. Subsequent detachment of the magnetic deflection system from the envelope, however, is impossible without destroying part of the deflection system, for example.
In the case of the RCA color-picture tube A67-610X, which is used, for example, in the Blaupunkt color TV receiver FM 100/27 inches, the envelope has a ring cemented thereto which carries along its circumference four slotted tongues spaced 90.degree. apart with the aid of which the magnetic deflection system is attached, and simultaneously adjusted, by means of screws. Thus, the magnetic deflection system can be separated from the envelope without difficulty, but adjustment is difficult because of four fastening screws must be turned at the same time.
In the case of Philips' inline color-picture tube A66500X of the 20-AX system, the deflection system is clamped to the neck of the picture tube. As the envelope there is provided a glass ring with whose side surfaces a preadjustment of the deflection system is achieved. Reference is made to a Valvo publication entitled "20 AX -- Vom Konzept sum System" and issued in February 1974. The deflection system is not mounted to this centering ring.